3-D electromagnetic modeling and nonlinear inversion

We describe a new algorithm for 3-D electromagnetic inversion that uses glo bal integral and local differential equations for both the forward and inve rse problems. The coupled integral and differential equations are discretiz ed by the finite element method and solved on a parallel computer using dom ain decomposition. The structure of the algorithm allows efficient solution of large 3-D inverse problems. Tests on both synthetic and field data show that the algorithm converges reliably and efficiently and gives high-resol ution conductivity images.